Train communications system involving fluid signal shielding means

ABSTRACT

A hollow metallic device surrounds an antenna fixed to the moving car of the train, and a substance, which absorbs or reflects electromagnetic wave energy, is discharged therefrom in two paths on either side of the leakage wave guide extending in the path of the car movement adjacent the track.

United States Patent [54] TRAIN COMMUNICATIONS SYSTEM INVOLVING FLUID SIGNAL SI-IIELDING MEANS 7 Claims, 3 Drawing Figs.

[52] US. Cl 325/52, 333/12, 343/713, 343/841 [51] Int. Cl 1104b 1/10,

[50] Field of Search 340/25 8, 258 C; 325/52, 53; 333/12; 343/71 1, 713, 716, 841, 842; 246/187 C [5 6] References Cited UNITED STATES PATENTS 2,206,923 7/1940 Southworth 340/258 (C) 2,580,155 12/1951 Brannen 340/258 (C) 2,702,342 2/1955 Korman 340/258 3,466,651 9/1969 Bigelow 325/51 (UX) Primary Exam iner- Richard Murray Assistant Examiner-James A. Brodsky Attorney Sughrue, Rothwell, Mion, Zinn and MacPeak ABSTRACT: A hollow metallic device surrounds an antenna fixed to the moving car of the train, and a substance, which absorbs or reflects electromagnetic wave energy, is discharged therefrom in two paths on either side of the leakage wave guide extending in the path of the car movement adjacent the track.

PATENTED JUN29 IBYI FIG.

PRIOR ART FIG. 2

FIG. 3

TRAIN COMMUNICATIONS SYSTEM ENVOLVING FLUID SHGNAL SHIELDING MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a communication system involving a moving vehicle and a stationary roadway over which the vehicle passes, and in particular, to a train communication system for communication through a leakage wave guide, a leakage coaxial cable or a line for the propagation of a surface wave constructed along the train track.

2. Description of the Prior Art Prior art railroad communication systems involve a leakage wave guide, leakage coaxial cable or a surface wave propagation line which extends parallel to the train track, to one side thereof, such that the moving railroad car which carries an antenna or the transmission or reception of signals moves in close proximity to the leakage wave guide, etc., but spaced slightly therefrom. A typical communication system for a railroad train is shown in Fig. I. The railroad or train car 1 moves relative to the tracks, indicated at 2, and the train car 1 carries an antenna 3 for signal transmission and reception. The antenna 3 overlies a leakage wave guide 4, for instance, which extends for a relatively large distance alongside the track 2. Repeaters and an end station, for instance, are inserted in the leakage wave guide at spaced locations and through these repeaters and end stations, command signalsfor train control and many other kinds of signals are transmitted to the train receiving station from the stationary track station. In communicating from the stationary station to the station carried by the train within car 1, for instance, a signal from the stationary station is converted to a microwave signal by a suitable device at the end station and is transmitted within wave guide 4 through the intermediary of repeaters.

A portion of the microwave signal transmitted inthe wave guide leaks out of the wave guide and propagates in the direction of the antenna indicated at 3 for reception by the end station on the moving train through this antenna, and hence, it is possible to perform communication between the stationary transmitter and the moving receiver on the train. It goes without saying that signals may be communicated from the train to a stationary station along the track through a communication path which is the reverse to that described above.

In general, the electromagnetic wave energy, which is radiated from the leakage wave guide 45, or the train antenna in a reverse communication system is not only received by the train antenna or the leakage wave guide which face each other, but in fact, such energy is radiated and scattered throughout the space in the vicinity of these elements, as shown by arrows 5, 6 and 7,.lFig. i. It follows from this that strong electromagnetic waves exist along the track and inflict electric wave noise on receivers other than the signals employed in train communication. Further, if the electromagnetic wave noise is strong, the frequency band or railroad communication as assigned in a rigid manner through rules and regulations concerning electric wave management becomes narrow. Further, with respect to this electromagnetic wave noise, in communicating from a stationary transmitting station to a moving train station, it is necessary to leak the signal uniformly from the leakage wave guide over a relatively long distance adjacent the track so that the available electromagnetic wave energy is extremely small and hence, the electromagnetic wave energy transmitted to other than the pick-up antenna is also relatively small. Namely, it is on the order of decibels per 1 meter of wave guide leakage. However, in communicating from a moving train station to a stationary receiver station, electromagnetic waves of several watts are radiated from a train antenna extending only several meters so that it follows from this that extremely strong electrornagnetic waves exist in the vicinity of the antenna 3 carried by the moving train car. Consequently, in this case, the reception trouble due to electromagnetic wave noise is considerable.

The present invention has an object to cancel out this defect and relates to train communication systems wherein a shield is provided for the electromagnetic wave energy in the neighborhood of the train antenna and the electromagnetic wave energy radiated from the train antenna is attenuated to an arbitrary value in comparison to the electromagnetic noise wave in the neighborhood of the track.

SUMMARY OF THE INVENTION This invention is directed to an electromagnetic wave energy shield carried by the moving railroad car for shielding the train antenna and discharging a substance which absorbs or reflects electromagnetic wave energy on either side of the antenna carried by the train, said material passing by gravity to opposed sides of the leakage wave guide which underlies the same.

Preferably, a metallic discharge device surrounds the antenna carried by the railroad car, extends the length thereof and discharges water, treated with sodium chloride, other liquids, such as liquid nitrogen, plasma or like gas, ionized gas, the powder of a sublimating solid, carbon dioxide gas and powder of such diverse materials as sodium chloride, carbon and iron, which stream of liquid gas or powdered material passes downwardly on each side of the longitudinally aligned but spaced railroad car antenna and underlying wave guide.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an end elevational view of a schematic representation of a prior art railroad train communication system.

FIG. 2 is a similar end view of a railroad train communication system employing the shielding means of the present invention.

FIG. 3 is a plan view of the communication system shown in Fig. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 2 and 3 of the drawings, like parts of the system have identical numerical designations, such as train car 1, tracks 2, antenna 3 and wave guide 4.

A metallic shielding substance discharging device 8, of inverted U-shaped cross-section, is coupled to the railroad car body in the form shown and surrounds the upper part and both sides of antenna 3. The metallic device 8 is so designed as to discharge, either under positive pressure or by gravity, a substance 9 which absorbs or reflects the electromagnetic wave energy. The substance 9 may comprise such diverse materials as water, particularly water incorporating in solution sodium chloride or the like, which absorbs electromagnetic waves effectively, a suitable liquid, such as liquid nitrogen, gases, such as plasma or the like, ionized gas, carbon dioxide gas, or gases or powders of a sublimating solid and more conventional powders, such as sodium chloride, carbon and iron.

Electromagnetic wave energy which is radiated from the train antenna is thus covered by the combined shields 8 and 9 so that it attenuates at the outside of these shields. Thus, the electromagnetic field in the vicinity of the track is weakened to some degree as is the electromagnetic wave energy leaking from, the leakage wave guide so that the electromagnetic wave noise decreases.

In the present invention, the electromagnetic wave energy radiated from the antenna is weakened because it is effectively covered or surrounded by a substance which acts as a shield .for the electromagnetic wave energy. Thus, the electromagemployed in the train'communication system. Further, since the shielding is quite effective, it is possible to employ relatively small electromagnetic fields and it is possible to use the wave energy of identical frequency for other purposes.

While the above invention has been described in conjunction with a leakage wave guide and a train carried antenna, the invention is not limited to such an arrangement and the shielding techniques of this invention may be used in railroad train communication systems employing the train carried antenna and a transmission line, such as a leakage coaxial cable, pair line, G-line and surface guide, as a substitute for element 4 of the system.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What we claim is:

I. In a communication system between a vehicle moving along a roadway having a stationary transmission line extending along the roadway and the path of the vehicle for transmitting an electromagnetic wave signal, and wherein said moving vehicle carries an antenna in close physical proximity to said transmission line, the improvement comprising: first shielding means carried by said vehicle for permanently partially surrounding said antenna for shielding the antenna from signals other than communication signals from said transmission line and a shielding material carried by said vehicle mmentarily partially surrounding portions of said transmission line.

2. The communication system as claimed in claim 1 wherein said first shielding means comprises a U-shaped metallic member which overlies the vehicle carried antenna in inverted fashion with the legs of the U-shaped metallic member extending downwardly on each side of said antenna and said transmission line underlying the antenna of the said moving vehicle.

3. The communication system as claimed in claim 2 wherein said U-shaped metallic member comprises a hollow casing and said shielding material comprises a fluid shielding material with the legs of said hollow casing discharging the fluid shielding material along paths on each side of said underlying transmission line.

4. The communication system as claimed in claim 3 wherein said fluid shielding material comprises one fluent material of the group consisting of water, a sodium chloride water solution, a liquid inert gas, ionized gas, plasma gas, a sublimating solid or gaseous product and powders of sodium chloride, carbon or iron.

5. The communication system as claimed in claim 1 wherein said first shielding means comprises a metallic reflector partially surrounding said antenna and said shielding material comprises a fluent substance discharged from said reflector along at least one side of a longitudinally aligned antenna and transmission line which fluent substance absorbs or reflects electromagnetic energy.

6. The communication system as claimed in claim 1 wherein said transmission line lies below and in longitudinal alignment with the antenna carried by said moving vehicle and said first shielding means comprises: a metallic member partially surrounding and overlying said antenna.

7. The communication system as claimed in claim 6 wherein said shielding material comprises a fluid shielding material discharged from said member and partially surrounding said transmission line. 

1. In a communication system between a vehicle moving along a roadway having a stationary transmission line extending along the roadway and the path of the vehicle for transmitting an electromagnetic wave signal, and wherein said moving vehicle carries an antenna in close physical proximity to said transmission line, the improvement comprising: first shielding means carried by said vehicle for permanently partially surrounding said antenna for shielding the antenna from signals other than communication signals from said transmission line and a shielding material carried by said vehicle momentarily partially surrounding portions of said transmission line.
 2. The communication system as claimed in claim 1 wherein said first shielding means comprises a U-shaped metallic member which overlies the vehicle carried antenna in inverted fashion with the legs of the U-shaped metallic member extending downwardly on each side of said antenna and said transmission line underlying the antenna of the said moving vehicle.
 3. The communication system as claimed in claim 2 wherein said U-shaped metallic member comprises a hollow casing and said shielding material comprises a fluid shielding material with the legs of said hollow casing discharging the fluid shielding material along paths on each side of said underlying transmission line.
 4. The communication system as claimed in claim 3 wherein said fluid shielding material comprises one fluent material of the group consisting of water, a sodium chloride water solution, a liquid inert gas, ionized gas, plasma gas, a sublimating solid or gaseous product and powders of sodium chloride, carbon or iron.
 5. The communication system as claimed in claim 1 wherein said first shielding means comprises a metallic reflector partially surrounding said antenna and said shielding material comprises a fluent substance discharged from said reflector along at least one side of a longitudinally aligned antenna and transmission line which fluent substance absorbs or reflects electromagnetic energy.
 6. The communication system as claimed in claim 1 wherein said transmission line lies below and in longitUdinal alignment with the antenna carried by said moving vehicle and said first shielding means comprises: a metallic member partially surrounding and overlying said antenna.
 7. The communication system as claimed in claim 6 wherein said shielding material comprises a fluid shielding material discharged from said member and partially surrounding said transmission line. 